Principle of Equivalence (对等原则) of Hardware and Software:
Any task done by software can also be done using hardware, and any operation performed directly by hardware can be done using software.（Assuming speed is not a concern.）
Measures (计量单位) of speed and capacity:
Kilo (千)- (K) = 1 thousand = 103 and 210
Mega (兆)- (M) = 1 million = 106 and 220
Giga (鲒)- (G) = 1 billion = 109 and 230
Tera (汰)- (T) = 1 trillion = 1012 and 240
Peta (帕)- (P) = 1 quadrillion = 1015 and 250
Exa (艾)- (E) = 1 quintillion = 1018 and 260
Zetta (泽)- (Z) = 1 sextillion = 1021 and 270
Yotta (娆)- (Y) = 1 septillion = 1024 and 280
Whether a metric refers to a power (幂) of ten (e.g., speed) or a power of two (e.g., capacity) depends upon what is being measured.
Hertz (赫兹) = clock cycles per second (frequency)
1MHz = 1,000,000Hz
Processor speeds are measured in MHz or GHz.
Byte (字节) = a unit of storage
1KB = 210 = 1024 Bytes
1MB = 220 = 1,048,576 Bytes
1GB = 230 = 1,099,511,627,776 Bytes
Main memory (RAM) is measured in GB
Disk storage (磁盘存储) is measured in GB for small systems, TB (240) for large systems.
Measures of time and space:
Milli (毫)- (m) = 1 thousandth = 10^(-3)
Micro (微)- () = 1 millionth = 10^(-6)
Nano (纳)- (n) = 1 billionth = 10^(-9)
Pico (皮)- (p) = 1 trillionth = 10^(-12)
Femto (飞)- (f) = 1 quadrillionth = 10^(-15)
Atto (唉)- (a) = 1 quintillionth = 10^(-18)
Zepto (沢)- (z) = 1 sextillionth = 10^(-21)
Yocto (妖)- (y) = 1 septillionth = 10^(-24)
Computers with large main memory capacity (主存容量) can run larger programs with greater speed than computers having small memories.
RAM is an acronym for random access memory (随机访问存储器). Random access means that memory contents can be accessed directly if you know its location.
Cache (缓存) is a type of temporary memory that can be accessed faster than RAM.
Standards Organizations 标准化组织
There are many organizations that set computer hardware standards -- to include the interoperability (互操作性) of computer components.
Some of the most important standards-setting groups are：
The International Organization for Standardization (ISO)
Establishes worldwide standards for everything from screw threads (螺纹) to photographic film (交卷、底片).
Is influential in formulating standards for computer hardware and software, including their methods of manufacture.在制定计算机硬件和软件标准，包括其制造方法方面具有影响力。
Note: ISO is not an acronym. ISO comes from the Greek, isos, meaning “equal.”
The Institute of Electrical and Electronic Engineers (IEEE)
Promotes the interests of the worldwide electrical engineering community.
Establishes standards for computer components, data representation, and signaling protocols, among many other things.
The International Telecommunications Union (ITU)
Concerns itself with the interoperability of telecommunications systems, including data
communications and telephony.
National groups establish standards within their respective countries:(国家团体在各自国家内制定标准：)
The American National Standards Institute (ANSI)
The British Standards Institution (BSI)
中国国家标准化管理委员会（由国家市场监督管理总局领导）
Historical Development 发展历程
Generation Zero: Mechanical Calculating Machines (机械计算机) (1642 - 1945)
The First Generation: Vacuum Tube Computers (真空管计算机) (1945 - 1953)
The Second Generation: Transistorized Computers (晶体管计算机) (1954 - 1965)
The Third Generation: Integrated Circuit Computers (集成电路计算机) (1965 - 1980)
The Fourth Generation: VLSI Computers (超大规模集成电路计算机) (1980 - ????)
Moore’s Law (摩尔定律，1965) :Gordon Moore, Intel founder
“The density(密度) of transistors in an integrated circuit willdouble every year.”
Contemporary （当代/现代） version:
“The density of silicon chips（硅芯片）doubles every 18 months.”
But this “law” cannot hold forever ...
Rock’s Law (洛克定律) :Arthur Rock, Intel financier
“The cost of capital equipment (资产设备) to build semiconductors（半导体） will double every four years.”
In 1968, a new chip plant cost about $12,000.
At the time, $12,000 would buy a nice house in the suburbs.
An executive (高管) earning $12,000 per year was “making a very comfortable living.”
In 2012, a chip plants under construction cost well over $5 billion.
$5 billion is more than the gross domestic product of some small countries, including Barbados (巴巴多斯岛), Mauritania (毛里塔尼亚), and Rwanda (卢旺达).
The Computer Level Hierarchy 计算机层次结构
Each virtual machine layer is an abstraction of the level below it.
The machines at each level execute their own particular instructions, calling upon machines at lower levels to perform tasks as required.
Computer circuits ultimately carry out the work.（计算机电路最终完成了这项工作）
Level 6: The User Level (用户层)
Program execution and user interface level.
The level with which we are most familiar.
Level 5: High-Level Language Level （高级语言层）
The level with which we interact when we write programs in languages such as C, Pascal, Lisp, and Java.
Level 4: Assembly Language Level (汇编语言层)
Acts upon assembly language produced from Level 5, as well as instructions programmed directly at this level.
Level 3: System Software Level (系统软件层)
Controls executing processes on the system.
Protects system resources.
Assembly language instructions often pass through Level 3 without modification.（汇编语言指令通常不经修改就经历level3）
Level 2: Machine Level (机器层)
Also known as the Instruction Set Architecture (ISA) Level.
Consists of instructions that are particular to the architecture of the machine.
Programs written in machine language need no compilers, interpreters, or assemblers (汇编程序).
Level 1: Control Level (控制层)
A control unit (控制单元) decodes and executes instructions and moves data through the system.
Control units can be microprogrammed (微程序的) or hardwired (硬接线的).
A microprogram is a program written in a low-level language that is implemented by the hardware.
Hardwired control units consist of hardware that directly executes machine instructions.
Level 0: Digital Logic Level (数字逻辑层)
This level is where we find digital circuits (the chips).
Digital circuits consist of gates and wires.
These components implement the mathematical logic of all other levels.